It is known that the pulp of teeth react to sufficiently strong irritations—e.g., caries, trauma, or preparatory measures—with inflammations. These and other reasons may make a root canal treatment necessary. Independently of which method is used for the later therapeutic or prophylactic root filling, it is first necessary to open the tooth, including the pulp, using mechanical (e.g., drills) and chemical means.
The known preparations of the root canal relate to the expansion, cleaning, and shaping of the root canal, in particular through a biomechanical preparation, which particularly comprises filing and flushing the root canal until it is essentially absolutely shaped and cleaned. The root is subsequently filled, it being the goal of the root filling to hermetically seal the entire canal system as permanently as possible, to prevent the penetration of microorganisms or liquids after the treatment.
Various techniques are available to those skilled in the art for the root filling. One known technique is, for example, so-called lateral condensation, in which a long gutta-percha point—which fills up the tooth canal—coated with sealer is introduced into the previously prepared canal. By spreading and the insertion of further gutta-percha points, the channel is filled nearly completely. The lateral condensation of the accessory points allows an increase in density of the gutta-percha filling in this case, which is only possible in a very time-consuming manner, however. A further problem arises if too much sealer is applied to the gutta-percha point syringe or if excess sealer is used in general, because in this case the danger of overstuffing arises. The excess sealer material then squeezes out at the end of the root and intercalates in the surrounding bone.
A further tooth filling method comprises the use of thermoplastic filling material (THERMAFILL material, Dentsply Maillefer, Ballaigues, Switzerland). For the thermoplastic filling material it is necessary for a conically prepared channel to be available in the tooth, and for an intact apical terminus of the tooth to be provided—for example, by the introduction of sealer. However, these requirements for the thermoplastic filling material also simultaneously describe the decisive disadvantage of this method, because sealer may easily be pressed out beyond the apex. In this way, the cement material is pressed into the tissue surrounding the tooth and permanently intercalated. Undesired rejection reactions in the tissue or cyst formation may occur due to the intercalated cement material.
A further known method is thermoplastic condensation. The requirement for this is an intact and narrow apical foramen. In this method, a specially adapted gutta-percha point is plasticized by friction heat on the canal wall. The gutta-percha is rubbed apically and on the canal wall. The danger of overfilling with sealer also exists in this method.
In addition, those skilled in the art have the option of treating the root canal by a thermoplastic injection, in which gutta-percha heated outside the mouth is introduced into the canal using an injection syringe. Because the gutta-percha is introduced in the liquid state, the danger of overstuffing also exists here, by which gutta-percha material is introduced into the surrounding tissue beyond the tooth canal. A further disadvantage of this method is that an intact apical foramen must always be available as a requirement for a successful root filling.
All known methods share the feature that the filling material used may be pressed out of the root canal into the surrounding tissue due to the danger of overstuffing. In this way, inflammations and/or cyst formation may be initiated, which result in bone substance loss and significant pain for the patient. Moreover, a further main problem is the oval (at least nonround) shape of the apical foramen. Leaks thus arise in a filling system which has a round shape. Once these disadvantages have occurred, a revision of the entire method is necessary, and/or a root tip resection and/or the extraction of the tooth. Treatments of this type are connected with high costs and/or operative interventions.